Ibn Ezra

[Beside] streams (פַּלְגֵי - palgei): From the same root as (Genesis 10:25) "divided" (peleg) [referring to dividing/channeling water]. Beside streams of water (עַֽל־פַּלְגֵי־מָ֥יִם - al palgei mayim): Means beside one of the streams. Similar [constructions where a plural denotes one instance within a category include]: "to the innermost parts (yarketei - plural construct) of the ship" (Jonah 1:5) [referring to one area]; "and he was buried in the cities (be-arei - plural construct) of Gilead" (Judges 12:7) [meaning in one city]; "son of she-asses" (atonot - plural) (Zechariah 9:9) [likely referring to the foal of one specific donkey]. And some say (v'yesh omrim): That the meaning of "its fruit" (piryo) is analogous to "children of youth" (Psalm 127:4) [interpreting the fruit metaphorically as descendants]. Whose foliage never fades (וְעָלֵ֥הוּ לֹֽא־יִבּ֑וֹל - ve-alehu lo yibol): [This represents] his wealth (oshro) enduring all his days, in the sense of (Ecclesiastes 7:11): "Wisdom is good with an inheritance" [implying enduring substance]. And whatever it produces thrives (וְכֹ֖ל אֲשֶׁר־יַעֲשֶׂ֣ה יַצְלִֽיחַ - ve-khol asher ya'aseh yatzliach): This refers back to the person (ha-adam) who is compared to the tree. And some say (v'yesh omrim): That the phrase "whatever it produces thrives" refers back to the tree itself – meaning that if a branch (sa'if) is taken from it and planted, it will thrive. And others have said (v'acherim amru): That it refers back to "its foliage" (alehu), similar to (Ezekiel 47:12) "and its foliage shall be for healing" [li-trufah - implying the leaf itself produces a successful outcome]. And according to my opinion (u-lefi da'ati): The meaning of "its fruit" (piryo) is the wise soul (ha-neshamah ha-chakhamah) that will be filled with God's Torah, enabling it to recognize its Creator and His deeds which endure forever. It [the soul] will cleave to its supernal world upon separation from its body, like ripened fruit on a tree that separates from it and no longer needs it – for the tree existed for the sake of the fruit. "Whose foliage never fades" (ve-alehu lo yibol) [represents] his good reputation (zikhro ha-tov), in the manner of (Proverbs 10:7) "The memory of the righteous is a blessing" (zekher tzaddik li-verakhah). "And whatever it produces thrives" (ve-khol asher ya'aseh yatzliach) [refers to worldly success:] wealth (hon), children (banim), and honor (kavod).